The coupling of a semi-mounted trailer on a tractor generally occurs by backing up the tractor underneath the trailer, whereupon a king pin arranged on the underside of the trailer engages with a fifth wheel located on the tractor and is then locked. For the uncoupling, the trailer is parked in usual manner, the fifth wheel is opened, and the tractor is driven out. To optimize the working conditions of long-haul drivers, there are efforts to automate the coupling and uncoupling of the trailer and the truck or to control this process remotely from the driver's cabin of the truck. In connection with such remotely controllable fifth wheels, there are already systems in existence that undertake the connecting of supply lines between tractor and trailer in automated manner, along with the coupling and uncoupling of the trailer. By supply lines is meant primarily cables for transmission of electrical energy, but also pneumatic or hydraulic lines.
A proven system for connecting the supply lines by a coupling of the trailer comprises a wedge connector that is pivoted on the king pin, per DE 101 55 056 A1, which fits into the wedge-shaped entry opening when the king pin is introduced into the fifth wheel, where it mates with plug contacts. When the tractor drives along curves, the wedge connector is form-fitted in the entry opening and turns relative to the trailer. For this reason, it is necessary to provide a sufficient length of supply line at the trailer side, in order to avoid a breaking of the supply line between the wedge connector and the fifth wheel when negotiating a tight curve. The main drawback, which leads to systematic failures, is that the supply line hangs down when driving on a straight stretch of road and thus there is a risk of damage or breaking.
In order to avoid damage to supply lines between a tractor and a trailer, so-called line magazines are already known from the prior art, which maintain the connection line under a tensile stress by means of a spring-loaded cable drum. One such line magazine is disclosed, for example, in DE 817 556 B and comprises a housing with a cable drum mounted therein, able to turn on a hollow axle. The connection line in the noncoupled condition is wound up until the connector touches the housing. The portion wound onto the cable drum is connected to a fixed cable segment led out through the hollow axle via a flat cable connected to both parts. However, this design has proven to be unreliable in daily use, since the use of three cable segments with two connection sites has led to breakages.
For this reason, the basic problem of the invention was to provide a robust line magazine, which prevents the supply line from hanging down in a mechanically simple way, while on the other hand it provides a constant pretensioning of the supply line.